Water-saute onions and peppers, add sweet potatoes, tomatillos, spices, beans, tomatoes, corn and cilantro. Simmer for 30 minutes or until potatoes are cooked through. Add a small amount of water if mixture gets too dry. Spray a baking pan (see note) lightly with cooking spray if not nonstick. Place a small amount of chili mixture on bottom, then layer 6 tortillas, chili mixture, remaining tortillas and remaining chili mixture. Sprinkle with pumpkin seeds and non-dairy cheese if using. Bake at 350 degrees F for 25-30 minutes. Serve with guacamole and salsa, if desired.